Paper Chromatography

DATED: September 16TH, 2009

EXPERIMENT# OBJECT: TO OBSERVE THE SEPARATION OF A MIXTURE BY THE METHOD OF PAPER CHROMATOGRAPHY.

REQUIREMENTS:

Mixture obtained by column chromategrapghy by rose, filter paper of 8/3 size, pencil, paper chromatography apparatus, solvent, uv chamber, capillary tubes, scale

THEORY: PAPER CHROMATOGRAPHY DEFINITION Paper chromatography is an analytical chemistry technique for separating and identifying mixtures that are or can be coloured, especially pigments by the flow of solvent on a filter paper.

ADVANTAGES AND DISADVANTAGES • •

• • •

This technique provides an easy way to separate the components of a mixture. in analytical chemistry, technique for separating dissolved chemical substances by taking advantage of their different rates of migration across sheets of paper. It is an inexpensive but powerful analytical tool requires very small quantities of material Paper chromatography is a useful technique because it is relatively quick

PHASES In paper chromatography, the stationary phase is a very uniform absorbent paper. The mobile phase is a suitable liquid solvent or mixture of solvents.

THE ESSENTIAL STRUCTURE OF PAPER Paper is made of cellulose fibres, and cellulose is a polymer of the simple sugar, glucose. The key point about cellulose is that the polymer chains have -OH groups sticking out all around them. To that extent, it presents the same sort of surface as silica gel or alumina in thin layer chromatography. PAGE NO: ___ SIGNATURE:______________

TEACHER

DATED: September 16TH, 2009 It would be tempting to try to explain paper chromatography in terms of the way that different compounds are adsorbed to different extents on to the paper surface. In other words, it would be nice to be able to use the same explanation for both thin layer and paper chromatography. Unfortunately, it is more complicated than that! The complication arises because the cellulose fibres attract water vapour from the atmosphere as well as any water that was present when the paper was made. You can therefore think of paper as being cellulose fibres with a very thin layer of water molecules bound to the surface. It is the interaction with this water which is the most important effect during paper chromatography.

PAPER CHROMATOGRAPHY USING A NON-POLAR SOLVENT Suppose you use a non-polar solvent such as hexane to develop your chromatogram. Non-polar molecules in the mixture that you are trying to separate will have little attraction for the water molecules attached to the cellulose, and so will spend most of their time dissolved in the moving solvent. Molecules like this will therefore travel a long way up the paper carried by the solvent. They will have relatively high Rf values. On the other hand, polar molecules will have a high attraction for the water molecules and much less for the non-polar solvent. They will therefore tend to dissolve in the thin layer of water around the cellulose fibres much more than in the moving solvent. Because they spend more time dissolved in the stationary phase and less time in the mobile phase, they aren't going to travel very fast up the paper. The tendency for a compound to divide its time between two immiscible solvents (solvents such as hexane and water which won't mix) is known as partition. Paper chromatography using a non-polar solvent is therefore a type of partition chromatography.

PAPER CHROMATOGRAPHY USING A WATER AND OTHER POLAR SOLVENTS A moment's thought will tell you that partition can't be the explanation if you are using water as the solvent for your mixture. If you have water as the mobile phase and the water bound on to the cellulose as the stationary phase, there can't be any meaningful difference between the amount of time a substance spends in solution in either of them. All substances should be equally soluble (or equally insoluble) in both.

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TEACHER

DATED: September 16TH, 2009 If water works as the mobile phase as well being the stationary phase, there has to be some quite different mechanism at work - and that must be equally true for other polar solvents like the alcohols, for example. Partition only happens between solvents which don't mix with each other. Polar solvents like the small alcohols do mix with water..

INTERPRETING THE DATA The Rf value for each spot should be calculated. Rf stands for "ratio of fronts" and is characteristic for any given compound. Hence, known Rf values can be compared to those of unknown substances to aid in their identifications.

(Note: Rf values often depend on the temperature, solvent, and type of paper used in the experiment; the most effective way to identify a compound is to spot known substances next to unknown substances on the same chromatogram.) In addition, the purity of a sample may be estimated from the chromatogram. An impure sample will often develop as two or more spots, while a pure sample will show only one spot.

PRINCIPLE This technique proceeds by a partly partition (distribution) and partly adsorption mechanism. The constituents of the mixture are distributed between the water held on the filter paper (water acts as a stationary phase) and organic solvent (mobile phase).

TYPES ASCENDING AND DESCENDING PAPER CHROMATOGRAPHY

Depending upon the direction of the solvent travel, paper chromatography is termed as ascending or descending type. When the solvent travels upward on the paper, it is termed as ascending paper chromatography and descending paper chromatography when the solvent travels in the downward direction.

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DATED: September 16TH, 2009

An experimental setup for paper chromatography

APPLICATION • • • • •

Chemical separations Widely used in protein and nucleic acid blotting Separating and identifying mixtures Chromatography is an important tool of the forensic chemist in solving crimes, DNA and RNA sequencing, among others. Paper chromatography is one method for testing the purity of compounds

PROCEDURE THE PROCEDURE IS SASME AS THIN LAYER CHROMATOGRAPHY INCLUDING SO NOT WRITING DETAILS IN FOLLOWING PROCEDURE

In this procedure, a drop of the test solution is applied as a small spot near one edge of the filter paper and the spot is dried. Then, the end of the paper strip is dipped into a developing solvent. The liquid is sucked up through the capillaries of the paper; it reaches the mixture and removes its components at various speeds. After the solvent front has reached a suitable height (15-20 cm), the paper is dried. The separated components are made visible with a suitable reagent called 'visualization reagent'. HERE WE HAVE USED UV CHAMBER FOR VISUALIZATION

The movement of any compound relative to the solvent is determined by the measurement of RF values, viz.,

Then,

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DATED: September 16TH, 2009

Pictorial representation of RF value

ROSE PHARMACOGNOSTIC FEATURES: BOTANICAL NAME: FAMILY:

ROSA

ROSEACEAE

ENGLISH NAME: ROSE LOCAL NAME: gulab PARTS USE: FRUIT, BARK, leaves CONSTITUENTS: Roses contain vitamin C , pectin, malic & citric acids, and antioxidant flavonoids, TANNINS ACTIONS: Mildly astringent, aperient, carminative, and refrigerant, cardiac tonic. Antidepressant, Feminine scent, antiseptic essence.

Uses •

• • •

•

Roses are popular garden shrubs, as flowering shrubs. They are also grown as cut flowers, as one of the most popular and commonly sold florists' flowers. A roses are grown for scented foliage Roses are also of great value to the perfume industry. An attar of roses is distilled from the flowers. The rose hip, the fruit of some species, is used as a minor source of Vitamin C. Roses may also be planted as hedging, and for game cover.

MEDICINAL USES

Because of the medicinal properties of rose, it is widely used in Ayurveda medicine. One cup of fresh rose hips has the equivalent amount of vitamin C in 60 oranges. Rose tea (tea made with rose petals and hips) is not a new idea. Here are 10 extraordinary health benefits of rose tea. PAGE NO: ___ SIGNATURE:______________

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DATED: September 16TH, 2009

Why roses are considered an ideal gift to express love? There is an interesting reason for this. Roses soothe heart and emotions. They also balance the mind. The reasons for the diuretic effects of the roses are they contain Vitamin C, pectin, malic and citric acids. 1. It clears toxins and heat from the body. As a result it has a cooling effect on the body. 2. It can relieve from sore throat, runny nose and blocked bronchial tubes 3. It is useful to people those prone to chest problems by fighting against infections 4. Rose tea helps to fight the infection in the digestive tract and re-establish the normal bacterial population of the intestines 5. It relieves fluid retention and hastens the elimination of wastes through kidneys 6. It is a wonderful remedy for dysentery, diarrhea and gastro enteritis 7. It is a laxative. It works as a remedy for all liver problems including sluggishness and constipation. 8. It cleanses the liver and gall bladder and promotes bile flow 9. Rose petal tea can be used to relieve uterine congestion causing pain and heavy periods. It is an excellent remedy for irregular periods and infertility. 10. It has an uplifting effect on the nervous system and can relieve insomnia, depression and fatigue

OBSERVATION

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DATED: September 16TH, 2009

RESULT

CONCLUSION

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